Capturing the Efficiency of a Melt-Mixing Process for Polymer Processing

Polymer blends and composite materials are often produced by a melt-mixing process using equipment specially designed to mix high-viscosity fluids during laminar flow. The melt-mixing process can be classified into distributive and dispersive mixing. Distributive mixing includes stretching and folding of fluid elements and re-arrangement of dispersed materials. Dispersive mixing is the size reduction of filler aggregates and/or liquid droplets in a matrix fluid. In order to optimize the design of a melt-mixing equipment, the evaluation of distributive and dispersive mixing is essential. In this paper, we consider fundamental aspects of melt-mixing, and experimental and computational approaches that have been reported in the literatures. Experimental observation of melt-mixing, by and large, provides rather limited information on the mixing process inside of equipment. Although a mixed material can be obtained under specified conditions and its physical properties can be directly measured, it is difficult for the mixing mechanism behind the final result to be inferred. Computational fluid dynamics complements this situation. Numerical simulation of a mixing process provides a non-invasive and detailed data in a equipment so that the quantitative measures for distributive and dispersive mixing can be obtained. We consider various quantitative measures that have been previously proposed to characterize distributive and dispersive mixing.